Methane may be converted to heavier liquids and hydrocarbons, such as methanol, formaldehyde, benzene, propanol and aromatics, by catalytic methane reforming reactions. The synthesis gas (also referred to as syngas) is a product of catalytic methane reforming reactions. Syngas may be produced by different methods including steam reforming of methane (SRM), dry reforming of methane (DRM), auto thermal reforming, and partial oxidation of methane. Steam reforming of methane is generally considered the more economical method, and is widely used for hydrogen production. However, this process presents some drawbacks, including a high ratio of hydrogen to carbon monoxide produced as the products of the reaction:CH4+H2O⇄CO+3H2  (steam reforming, SRM)
Since most processes, such as Fischer-Tropsch, use syngas as a feed in which the hydrogen to carbon monoxide ratio must be equal to 2, improvement of the hydrogen to carbon monoxide ratio seems to be necessary. One simple method for reducing the hydrogen to carbon monoxide ratio is separation of excess hydrogen from the syngas. Another method for improvement of the hydrogen to carbon monoxide ratio is the injection of carbon dioxide into the reforming feed, where the resulting reaction will be as follows:3CH4+2H2O+CO2⇄4CO+8H2  (combined dry-steam reforming, CRM)
In recent decades, the method of dry reforming of methane has attracted great attention from both industrial and environmental groups. It is noteworthy that the syngas produced by this method has a low H2/CO ratio.CH4+CO2⇄2CO+2H2  (dry reforming, DMR)
In catalytic methane reforming reactions, the active metal of the catalyst has a significant role in its activity. Two kinds of metals may be utilized as active metal catalysts including noble metals (such as platinum, rhodium and rhenium) and other non-noble metals (such as nickel).